Method of and apparatus for multiplex signaling



y 1930. E. F. w. ALEXANDERSON' 1,771,700

METHOD OF AND APPARATUS FOR MULTIPLEX-SIGNALING FiledJan. 8, 1925 RECEIVER INVENTOR ERNST. mmmmsou Wu 7 BY M Y /La and A ORNEY Patented July 29, 1930 UNITED STATES- PATENT OFFICE ERNST r. w. a ExAnnERson, or scnsuscrany, NEW YonK, ASSIGNOR To name CORPORATION OF AMERICA, A CORPORATION or DELAWARE METHOD OF AND' APPARATUS FOR IIIULTIPLEX SIGNALING Application filed January 8, 1925. -Serial No. 1,172;

This invention relates to a system of multiplex signaling, and particularly toa transoceanic system adapted for telephony or telegraphy.

In accordance withthe invention messages may be transmitted from a point or points on one side of a largebody ofwater, such,

for example, as theAtlantic Ocean to a point I of ultimate reception on the other side of the body of water by modulating and transmitting a plurality ofwaves of different frequencies respectively in accordance with different messages, receiving said plurality of waves at a point different from the pointof ultimate reception, modulating at said point 1 a wave of a still different frequency in accordance with said plurality of waves, and then transmitting the last-mentioned waves thus .modulated to the point of ultimate reception cated at Riverhead,yLong Island. In practicing the invention,,the waves used in transmitting the CllfIBIBIlU messages from the various'countries of Europe have been of com- "parative'ly low frequencies, and the transmitted waves have been received at a station located at Belfast, Maine, at which station they are received upon the same or different antennae and supplied to receivers tuned to the frequencies of the waves radiated from the European stations. The various receivers of the Belfast station are connected to a common antenna through a modulator, and the last-mentioned antenna is caused to radiatea wave .of differentfrequency from the firstmentioned waves, preferably a higher frequency of the'or'derzof upwards of 100,000

cycles persecondmodulatedin accordance with the waves to which. the respective receivers are tuned. I

An importantadvantage of the invention is 1 that the point, in the present instance, Belfast, Maine, at which the waves transmitted across theocean are firstrecei ved may be so located as to cause interference from static or other causes to be less than would be the case if the transoceanic messages were directly received at the point of ultimate reception; in this case the stationat Riverhead,Long

Island.

- Fig. 1 of the drawing indicates diagrammatically a number of transmitting stations which, for example, may beloc ated in different countries. I

Fig. 2 is a diagrammatic illustration of a combined receiving and transmitting station located at a point different from the point of ultimate reception of the messages transmitted by the different antennae of Fig. 1, and

Fig. 3 is a diagrammaticrepresentation of the receiving station at thepoint of ultimate reception. i

1 The transmitting stations shown in Fig. 1 and designated 2, 4 and 6 respectively may be located at the same or difierent points on the earths surface. .As one illustration of the use of the invention, the transmitting station 2. may be located in Germany and may transmit a series of wavesof24,0.00 cycles per second modulated in accordance witha telegraph or telephone: message"; the transmitting station' l. may be assumed to be located in England and to transmit a signal-modw lated wave of .a frequency of 21,300 cycles per second; and the transmitting station 6 may be taken as a station in France transinitting a signal-modulated Wave of a frequency of 21,000 cycles per second.

The arrangement of Fig. 2 comprises an antenna 8 which is preferably aperiodic and receivers 10, 12 and l l-tuned respectively to the difierent frequencies of the waves transmitted' from the stations 2, 4 and 6.. The outputs of the receivers 10, 12 and 14:. may next be supplied independently to vacuum tubes 16, 18 and 20 respectively, the output circuits of said tubes being coupledto a common circuit 22 which supplies currents of the different frequencies to which thereceiw ers 10, 12 and 14 are tuned to a modulator 24.

As shown in the drawing, the modulator 24 is of the well-known type kno wnas a Heising modulator. The modulator 24 supplies "to an antenna 26 coupled therewith a wave of'a.

frequency different from the frequencies of the Waves radiated from the transmitting stations 2, 4 and 6, and the wave radiated from the antenna 26 is modulated in accordance with the respective waves transmitted from stations 2, 4 and 6 and received by the receivers 10, 12 and 14 respectively.

A circuit arrangement such as is shown,

in Fig.3 may be employed at the point of ultimate receiption to receive the message transmitted from stations 2, 4 and 6 through -intermediation of a station having'an artransmitted from stations 2, 4 and 6, and there are provided on the output side of the detector 30, circuits 34, 36 and 38 tuned respec- .tively to the frequencies of the waves transmitted by stations 2, 4 and 6. Coupled with the circuit 34 is a circuit 40 including a detector 42, a heterodyne device 44 and telephones 46; coupled with the circuit 36 is 1 a circuit 48 including a detector 50, a heterodyne device 52 and telephones 54; and coupled with the circuit 38 is a circuit 56 including a detector 58, a heterodyne device 60 and telephones 62.

It was assumed above that transmitting stations 2, 4 and 6 might be stations in Ger many, England and France, transmitting frequencies of substantially 24,000, 21,300 and 21,000 cycles per second respectively. In the past it hasappeared preferable that frequencies of the order of 20,000-to 100,000 cycles per second be used in transmitting messages A across large bodies of water, such as the Atlantic Ocean, and where this invention has been employed, it has also seemed preferable to use for the carrier wave employed in the intermediate station shown in Fig. 2 a wave of a frequency of the order of upwards of 100,000 cycles per second. The invention, however, is not limited in its scope to such frequencies nor in its broadest aspects to the use in the station shown in Fig. 2 of a carrier frequency higher than the frequencies of the series of waves transmitted from the stations2, 4 and 6. On the contrary,.

f it is recognized that it may eventually be foundthat very short waves may advantageously be employed in transmitting messages over long distances, such as over oceans or other large bodies of water, and, therefore, stations 2, 4 and 6 may be utilized to transmit waves of very short length, and the station shown in Fig. 2 may utilize as a carrier waves of shorter length.

It is further recognized that various modifications may be made in the manner of utilization of this invention, and, accordingly, it is intended that nothing contained in the foregoing description shall be taken to limit the invention beyond the scope of the appended claims.

Having fully described my invention, what I claim is:

1. A method of multiplex signaling which consists in modulating at different points on the earths surface at a distance from each other, a plurality of waves of different frequencies adapted to transoceanic transmission in accordance with different messages to be transmitted to a common ultimate point of reception, transmitting said waves and receiving them ata distant point different from the pointof ultimate reception, modulating at said different point a wave of still different frequency, adapted to short distance radio transmission in accordance with all of said first-mentioned waves, transmitting said last-mentioned wave thus modulated to the point of ultimatereception and separately translating said different messages at the point of ultimate reception.

2; A method of multiplex signaling which consists in independently modulating a plurality of waves of difierent, comparatively low radio frequencies adapted to long distance radio transmission in accordance with different messages to be transmitted to a common ultimate distant point of reception, transmitting said waves'and receiving them at a distant point different from the point of ultimate reception, modulating at said different point a wave of a higher frequency adapted to short distance radio transmission in accordance with all of said first-mentioned waves, transmitting said last-mentioned wave thus modulated to the point of ultimate reception and separately translating said difsaid waves and receiving them at a transoceanic point different from the point of ultimate reception, modulating at said different point a wave of higher'frequency of the order of upwards of 100,000 cycles per second adapted to short distance radio transmission in accordance with all of said firstmentioned waves, transmitting said lastmentioned wave thus modulated to the point of ultimate reception and separately receiving said different messages at the point of ultimate reception.

4. A method of transoceanic multiplex signaling which consists in modulating at points on one side of the ocean at a distance from each other a plurality of waves of difierent frequencies respectively, in accordance with different messages to be transmitted to a common, ultimate point of reception on the other side of the ocean, transmitting said waves across the ocean and receiving them at p a point diflerent from the point of ultimate reception, modulating at said different point a wave of still different frequency in accordance with all of said first-mentioned waves, transmitting said last-mentioned waves thus modulated to the point of ultimate reception and separately translating said different mes sages at the point of ultimate reception.

In testimony whereof, I have hereunto subscribed my name this 6th day of January, 1925.

ERNST F. WV; ALEXANDERSON. 

